phpstan.org error on deep if -> for

[samsonasik]

Bug report

The issue is initially known from rector issue which uses call:

$this->nodeScopeResolver->processNodes($stmts, $mutatingScope, $nodeCallback);

ref rectorphp/rector#6900

Code snippet that reproduces the problem

Given the following code, in phpstan.org:

<?php declare(strict_types = 1);

class swThreads
{
    public function sort_comments_in_thread_array($comment, $thread_parentid = 0)
    {
        if ($thread_parentid)
        {
            if (isset($this->comments['#' . $comment['thread_parentid']]))
            {
                if (in_array('#' . $comment['parentid'], $lv1_keys))
                {
                    if (!$match)
                    {
                        for ($ii = 0;$ii < count($lv2_keys);$ii++)
                        {
                            if (!$match3)
                            {
                                for ($iii = 0;$iii < count($lv3_keys_all);$iii++)
                                {
                                    if (!$match4)
                                    {
                                        for ($iiii = 0;$iiii < count($lv4_keys_all);$iiii++)
                                        {
                                            if (!$match5)
                                            {
                                                for ($i6 = 0;$i6 < count($lv5_keys_all);$i6++)
                                                {
                                                    if (!$match6)
                                                    {
                                                        for ($i7 = 0;$i7 < count($lv6_keys_all);$i7++)
                                                        {
                                                            if (!$match7)
                                                            {
                                                                for ($i8 = 0;$i8 < count($lv7_keys_all);$i8++)
                                                                {
                                                                    if (!$match8)
                                                                    {
                                                                        for ($i9 = 0;$i9 < count($lv8_keys_all);$i9++)
                                                                        {
                                                                            if (!$match9)
                                                                            {

                                                                            }
                                                                        }
                                                                    }
                                                                }
                                                            }
                                                        }
                                                    }
                                                }
                                            }
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
                return true;
            }
        }
    }

}

Expected output

it works or show the errors.

[mergeable]

This bug report is missing a link to reproduction on phpstan.org.

It will most likely be closed after manual review.

[staabm]

I profilled this test-case. it seems there is no obvious low hanging fruit to optimize right now.

the general performance characteristics depend on the levels you nest the loops - not really suprising.

the deeper we nest the loops, the more variables the VariableTypeHolder contains and the longer takes it to merge the different Holders together, see the explosion of calls here:

I feel the only way forward would be to stop analysis at a certain level of nesting... not yet sure what this would mean for the overall result of the code beeing analyzed.

maybe it would make sense to conclude the analysis of such a method/function with a new NotAnalyzableType and report such type via a new rule, so user is getting aware that the nesting is a problem for phpstan, and therefore analysis cannot be done for it?

[staabm]

another idea: maybe it would make sense to reduce the number of LOOP_SCOPE_ITERATIONS the deeper we go into nesting.

so e.g. when analyzing more then 5 nested loops, reduce LOOP_SCOPE_ITERATIONS to e.g. 2?

Experimented on my laptop:

• Running the test-case with LOOP_SCOPE_ITERATIONS = 2 takes 20 seconds.
• Running it with LOOP_SCOPE_ITERATIONS = 3; takes 1min 40 seconds.

[ondrejmirtes]

Fixed by: phpstan/phpstan-src#2088

[samsonasik]

Thank you @ondrejmirtes, I believe it will speed up Rector as well.

[github-actions]

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